Coupled climate-carbon cycle models suggest that Amazon forests are vulnerable to both long- and short-term droughts, but satellite observations showed a large-scale photosynthetic green-up in intact evergreen forests of the Amazon in response to a short, intense drought in 2005. These findings suggest that Amazon forests, although threatened by human-caused deforestation and fire and possibly by more severe long-term droughts, may be more resilient to climate changes than ecosystem models assume.

We find no evidence of large-scale greening of intact Amazon forests during the 2005 drought – approximately 11%-12% of these drought-stricken forests display greening, while, 28%-29% show browning or no-change, and for the rest, the data are not of sufficient quality to characterize any changes. These changes are also not unique – approximately similar changes are observed in non-drought years as well.

But this week new research supports the original Amazongate version of the science. The Amazon may not be at risk from climate change. Researchers at Boston University, headed by Ranga B. Myneni, professor of geography and environment, found that satellite readings used by other scientists were based on contaminated data. In a paper published by Geophysical Research Letters, Prof. Myneni and associates say they found no evidence that the Amazon suffers extreme tree mortality, excessive forest greening or other trauma under extreme climate conditions.

The Myneni paper examined the impact on the Amazon of a major 2005 drought. Some scientists have argued that the 2005 drought caused significant rainforest disturbances. But Prof. Myneni says that science is based on satellite data that cannot be reproduced because much of it is “atmosphere corrupted.”

Don’t you love the way Corcoran describes greening as “significant disturbances” and implies that the earlier study found “extreme tree mortality” rather than geening?

But while Corcoran is being deceitful, you can’t blame this all on him.

[Amazon rain forests] may be more tolerant of droughts than previously thought

(Boston) — A new NASA-funded study has concluded that Amazon rain forests were remarkably unaffected in the face of once-in-a-century drought in 2005, neither dying nor thriving, contrary to a previously published report and claims by the Intergovernmental Panel on Climate Change.

The new Samanta study uses satellites to assess the colour of the rainforest canopy in the dry season of the year 2005, compared to the dry seasons of the years 2003 and 2004. More detected green colour in 2005 may suggest that the forest is being more productive (more green leaves photosynthesising), or more brown colours may suggest leaves dying and less productivity, than the previous years. The results show that 2005 was little different to the previous years, despite the strong drought.

This is important new information, as in 2007, a paper using the satellite-based same method showed a strong ‘greening-up’ of the Amazon in 2005, suggesting tolerance to drought. The new study shows that those results were not reproducible, but also highlight the extreme caution that should be attached to satellite studies generally in this field, with instruments in space collecting data which is then used to infer subtle changes in the ecology of tropical forests.

In contrast to the 2007 paper, Oliver Phillips, myself and others, published a paper in Science, using ground observations from across the Amazon, that while the 2005 drought did not dramatically change the growth of the trees compared to a normal year, as Samanta also show, but the deaths of trees did increase considerably. The new study of Samanta et al., supports the Phillips et al. study, which itself shows the Amazon is vulnerable to drought. The Phillips paper showed that remaining Amazon forests changed from absorbing nearly 2 billion tonnes of CO2 from the atmosphere a year, to being a massive committed source of over 3 billion tonnes, from tree mortality.

The evidence for the possibility of a major die-back of the Amazon rainforest is due to two factors,

That climate change induced decreases in rainfall in the dry season occur, and

The trees cannot tolerate these reductions in rainfall.

The Samanta paper does not directly address the first point, this is addressed using modelling. The second point is only addressed in a limited way. The critical question is how these forests respond to repeated droughts, not merely single-year droughts. The forests are of course able to withstand these single droughts (otherwise there would be no rainforest!) – it is their ability to survive an increased frequency of the most severe droughts that is critical to answer. Drought experiments, where a roof is built under the forest canopy, show that most forest trees survive a single year’s intense drought, but can’t persist with repeated years of drought. The Samanta study does not address this point at all.

In conclusion the new study lends further weight to the emerging picture of the 2005 drought, that tree growth was relatively unaffected, but tree mortality increased, contributing to temporarily accelerating the rate of climate change, rather than as usual reducing it via additions of carbon to the atmosphere from the dead trees. Furthermore, the climate change model results suggesting decreasing rainfall in the dry season over Amazonia in the coming decades are unaffected by the new study, thus overall the conclusions in the IPCC 2007 Fourth Assessment Report are strengthened (because the anomalous result of the Saleska 2007 science paper appear to be at fault), not weakened, by the new study as the press release implies.

The press release also states:

The IPCC is under scrutiny for various data inaccuracies, including its claim – based on a flawed World Wildlife Fund study — that up to 40% of the Amazonian forests could react drastically and be replaced by savannas from even a slight reduction in rainfall. …

“The way that the WWF report calculated this 40% was totally wrong, while [the new] calculations are by far more reliable and correct,” said Dr. Jose Marengo, a Brazilian National Institute for Space Research climate scientist and member of the IPCC.

I contacted Marengo to see if this fairly represented his position, and, no it didn’t, having been taken out of context. He wrote:

I did not know that Sangram would pass my comments for a blog.

I have exchanged few emails with him, and I agree with him about
his position on the greening of Amazonia as shown by Saleska et
al (2007). However, I have questioned him few times about his
conclusions on the IPCC 40% value. In his paper he does not show
anything that go against the 40%, and he did not mention IPCC at
all. So this comparison is out of of context considering the
finding of this high quality paper.

What I said is that the 40% was obtained qualitatively from a
map from Nepstad et al (2004), comparing the area burn during the
El Nino 1998 and the mean area. Nepstad considered the El Nino 1998
situation as an analogue of what the future could be, which may
not be entirely realistic. I said that between an eye calculation
to get the 40% reported by the WWF document and the calculations
from Samanta et al (2010), even though they refer to different things,
Samanta et al did more correct and reliable work.

Yes, I believe that the Amazon forests are vulnerable to rainfall
reduction, and high temperatures, and this would lead to what some
studies call the Amazon die back. However, the die back is still
somewhat uncertain, but without reaching a level in which the forest
would replaced by savanna, the forest is highly vulnerable to drought.

Perhaps it’s like “it’s always good news for the Republicans” in US politics. No matter what happens – or does not happen, or even when the opposite subsequently happens – quite a few “news” outlets will report that it’s good news for the Republicans.

It’s frustrating to see the ‘bad news for the IPCC’ appearing so frequently – unsurprising, because it seems to be a heavily-laden bandwagon – but frustrating. I’m reminded of an encounter I had with a prominent (if that’s the word) Intelligent Design creationist in 2007 who insisted that the Dover Trial, which fairly comprehensively destroyed the case for ID being taught in US schools, was actually a win for ID supporters and made ‘Darwinists a laughing stock’.

It was the first time I’d seen firsthand the extent to which people are willing to interpret a finding in their favour. Even when it’s completely opposite to their position, it can still be spun around if you aren’t concerned about accuracy!

The reporting by Corcoran and Leake should come as no surprise I guess, but what’s up with the press release? Why would they misrepresent their own researchers? What do the authors themselves think about it? Which is the blog post that Marengo is referring to? Does the website of Sangram Ganguly have the most annoying method of navigation ever? These are but a few questions I’m asking myself, and you.

It’s almost as if all these journalists and media employees don’t care for the truth or reality of anything they write. It’s almost as if they deliberately serve massively powerful and wealthy corporate and political interests by spinning and obfuscating.

Can that be right?

If that were true then everyone who ever took a paycheck from Rupert Murdoch would be implicated.

Yes, but the journalists involved are all doing what they would normally do. What’s disturbing about this case is that the press release itself is misleading. If you can’t trust the university behind the study…

> … what’s up with the press release? Why would they misrepresent their own researchers?

The university press offices are there to generate publicity and given that the people working in these departments have to deal with research from a very wide spectrum of disciplines, they can’t be expected to understand everything. As a result, every once in a while you get someone grabbing the wrong end of the stick and the journalists get fed bum information. But having said all that, the researchers are normally supposed to get the final say on the content of press releases, so it’s possible Samanta may have something to answer on this matter.

At the bottom, last quote, second to last paragraph, last sentence. “raliable” should be “reliable”.

Incidentally, I hadn’t thought of the fact that rainforests would be more vulnerable due to increased frequency of droughts — and that this would have a bearing on the interpretation of this particular study. That helps.

Another thing worth keeping in mind is that drought dieback will be more pronounced at the edges of a forest — for a number of reasons. What little greening this study showed occurred at places distant from the edges. Not as important as consecutive years of drought, though. Currently having a little difficulty finding the images, but it would be interesting to overlay the 10% “greening” that occurred with a map of the Amazon river — given Liebig’s law of the minimum.

Given the coverage issues, perhaps you should be concerned that this post will be distributed as “Tim Lambert says it’s always bad news for the IPCC” with no further elaboration by someone misusing it while launching into other reports attempting to discredit the IPCC.

About bloody time! In all the debate I am continuously confused as to why leaders of the Worlds major scientific institutions do not speak up in defence of science and scientists. I hope that this is the first step in a decision by the CSIRO to cease being a doormat for denialists.

If only the rest of the Worlds major scientific institutions would start effectively responding robustly to lies and slander. They don’t need to get on TV and debate trolls. They need to start issuing specific targeted media releases so the public knows where they stand on this.

Re #21: Try 15 my, chubbo [per Tripati et al. (2009)]. If you’re quoting Rees accurately, he’d be referring to the ice cores, and even those now go back about 800 ky. For a graph, you know how to find Wikipedia. Tell me, is the fat entirely between your ears?

“Prof. Myneni supports the basic IPCC climate science theory. But he said in an interview yesterday that the IPCC was being “alarmist” when it took the WWF research and produced a report that projected that 40% of the Amazon could be devastated and reformed by even a slight reduction in rainfall.”

I am going to contact Myeni to see if that is indeed what he said.

Also, research in the boreal forest of Canada is similar to that of findings made by Lewis. Specifically, during an extreme drought year the NDVI values over the forest were lower, but the real impact oft he drought was observed over subsequent one or two growing seasons when high mortality rates were observed. See work by Dr. Hogg.

Impacts of a regional drought on the productivity, dieback, and biomass of western Canadian aspen forests. 2008. Hogg, E.H.; Brandt, J.P.; Michaelian, M. Canadian Journal of Forest Research 38(6): 1373-1384.

So if the recent paper only limited the scope of study to 2005 (year of drought), then they could have missed significant response of the forest tot he 2005 drought in subsequent growing seasons. Also, what about the impact on the canopy of multi-year droughts?

Corcoran is disseminating misinformation and misrepresenting the science, again. And it will be interesting to see what Dr. Myeni says about how he was quoted.

I also encourage people to email Corcoran and the editor to let them know of what you think about Corcoran frequently misrepresenting the science and scientists.

Interestingly, it seems that Samanta himself has waded into the debate over at Realclimate and is defending the tone of the press release. However, he really doesn’t do himself any favours because the two reasons he gives as justification were already quite effectively debunked in the article he is commenting on, and he offers no further discussion.

Yes, especially when you use the term “denialist” with the specific intent of invoking the spectre of Holocaust denial

This tired old horse should be put out to pasture. People just laugh when they see it, and assume you are having a day when people see you for what you are — liars in the service of the filth merchants or unhinged moronic dupes.

How did a three-month dry spell get confused with a climate regime change — was the confusion only in the university press office’s press release and author’s Realclimate post, or was the actual paper confusing weather and climate?

@ 46 Tut,tut, poor sod. So vacuous and lame that s/he has to resort to vitriol and invective. That is all they have now.

Oh and @46, unless you are bouncing your IP, Tim can track you down if need be (e.g., if you start making threats), so best settle down, and as difficult as it is, try and bring something more substantive to the table that the nonsense you have been spouting above.

…and IIRC that means that ice mass is not being replenished at anywhere near the same rate it used to (IIRC as is happening with many glaciers too). If that keeps going for long enough it will be bad news.